1. Field of the Invention
The present invention relates to a process in the manufacturing of semiconductors. More particularly, the present invention relates to a treatment process capable of improving the quality of a deposited layer in a selective deposition.
2. Description of Related Art
In the manufacturing of semiconductors, selective deposition is often used to form different material layers, each having a desired thickness so that time-consuming and costly lithographic operations can be eliminated. For example, in the fabrication of the source/drain region of a MOS device having a shallow junction design, selective deposition deposits a silicon (or germanium) layer above the source/drain region to form a raised source/drain terminal. The raised source drain terminal is capable of preventing a junction leakage that results from the removal of a portion of the silicon material from the shallow junction layer above the source/drain region in a subsequent metal silicide reaction.
However, due to atmospheric oxidation, a native oxide layer having a non-uniform thickness but averaging at about 20 .ANG. is generally formed over the surface of a silicon layer. Hence, when a material is deposited over the silicon layer by selective deposition, dislocation, stack faults, uneven distribution and insufficient selectivity of the deposited material layer often occur. In brief, native oxide is a major drawback for selective deposition of material layers.
The conventional method of removing the effect due to the presence of a native oxide layer includes implanting boron difluoride ions BF.sub.2.sup.+ into the silicon substrate before carrying out the selective deposition of silicon (germanium) over the source/drain region. However, since an ion implantation may change the electrical properties of the substrate, the treatment can be applied to prime either a NMOS or a PMOS transistor, but not both. Furthermore, ion implantation and the selective deposition of silicon (germanium) cannot be carried out in the same reaction chamber, thereby adding some complications to the processing method.